Performance optimization opportunities in Analyzer

[lrytz]

Identified by @retronym scala/scala#6075 (comment)

---

https://github.com/scala/scala-asm/blob/v5.1.0-scala-2/src/main/java/scala/tools/asm/tree/analysis/Frame.java#L623-L632

• Type.getArgumentTypes(desc).length / Type.getReturnType(desc) == Type.VOID_TYPE could be directly implemented without constructing a Type isntance
• The same can be done in the Scala compiler (https://github.com/scala/scala/blob/v2.12.3/src/compiler/scala/tools/nsc/backend/jvm/analysis/InstructionStackEffect.scala#L63-L64)

---

In Type.java, a number of String to char[] conversions are performed to call into getType. If this method was duplicated to operatoe on String directly, those conversions could be avoided.

public static Type getReturnType(final String methodDescriptor) {
        char[] buf = methodDescriptor.toCharArray();
        return getType(buf, methodDescriptor.indexOf(')') + 1);
    }

Could use lastIndexOf to search from the end of the descriptor.